You get a hell of a-lot of R&D, talent infrastructure and pretty much anything for $16B think Facebook with its engineering talent would find it fairly trivial to replicate the tech. The big consumer internet acquisitions are very rarely about the technologies and more about the installed user base.

Plus other similar apps like Wechat, Line etc are more advanced.

And what's the point of it? They already have a working push messaging infrastructure for 1+ Billion people.

Yeah, at a minimum they should have been able to lower the price by threatening to make the exact WhatsApp functionality a subset of Facebook.

(A page out of Microsoft's play book.)

Edit: The Facebook Messenger has the features of WhatsApp already?! News to me, so you have a point re FB advertisement. :-)

Well it is already. The Facebook Messenger app. They bought Beluga in 2011 who produced that app originally. It's just that Facebook seems to have no Marketing folks, nor budget, nor strategy. So it never caught on and Whatsapp sailed past.